In recent years, the conventional oblong bathtub has undergone revoluntionary design changes. At the present time, commercial tubs are available in many different shapes and depths, and are optionally equipped with hydrotherapy systems that circulate water from the tub through nozzles, or "jets", located in the side walls of the tub. The force and swirling action of the water through the jets impart a soothing and therapeutic effect to the user.
Some bathtubs are manufactured in a factory location and shipped to the job site for installation. These units are made in standard, predetermined sizes, and are usually ordered from sales catalogs. However, with the growing popularity of very large tubs, sometimes referred to as "Roman" tubs, different manufacturing techniques have been required.
Since many of the large bathing vessels hold a ton or more of water, these tubs have been fabricated from waterproofed concrete. The great weight and risk of damage to factory-formed concrete tub shells has rendered prefabrication of these tubs impractical, and it has been necessary to form these tubs on the job site (i.e., in the exact location in the residence or lodging unit where the tube is desired).
For onsite forming of large vessels, a form is first constructed from wood to the desired shape of the vessel, and steel reinforcing bars are placed in the form. Next, the plumbing is set in place in the forms. The concrete is mixed and poured; after the concrete has set, the wood forms are stripped away. Then the inner surface of the concrete is sealed with an asphalt material, and the surface finish (tile, marble, or the like) is set in place.
This construction technique creates a number of difficulties. Firstly, the use of concrete on upper floors in a building imposes an extremely heavy weight load on the building when the tub is full. Therefore, expensive structural changes must be made to accomodate this weight. Though heavy, the concrete wall is nonetheless relatively thin and porous, with the possibility of cracking due to a shift in the building foundation. Plumbing problems or leaks in the concrete shell are difficult to locate and repair, since much of the vessel would have to be hammered away to make the repair.
Possibly the biggest difficulty with the poured-in-place concrete tub is associated with the logistics of the construction operation. Building of the tub, which is a relatively small part of any overall construction project, requires different workers from the carpentry, plumbing, steel, roofing (for asphalt sealing), tile, and electrical trades. Each worker must perform a relatively small function in the construction of the bath; if one worker does not show up on time, all others are delayed. The work is difficult on site because the workers are confined to a relatively small area, and other building activity is also going on in the same area. Therefore, it is desirable to remove as much of the tub construction work as possible away from the job site.
Therefore, it is an object of the invention to provide a base for a large bathing vessel which may be fabricated in a factory. It is another object of the invention to provide a method of manufacturing a bathing vessel which enables the vessel to be easily custom manufactured in a factory location to fit the particular specifications of a job site. It is another object of the invention to provide a custom bathing vessel which is relatively strong and lightweight, but which need not be fabricated from concrete. These and other objects of the invention shall be more fully illustrated in the following detailed description of the invention.